The primary objective is to elucidate the mode of action of antipsychotic and psychotomimetic drugs in the CNS and to study influences of neurotransmitter systems on dopamine (DA) neurons with the goal being to develop new type of antipsychotic drugs (APD's) with minimum neurological side effects. There are three specific aims for the coming year: 1. To continue studies of long-term effects of antipsychotic and psychotomimetic drugs on catecholamine system. 2. To continue studies of influences of neuroregulator systems on identified DA neurons. 3. To continue studies on the functional significance of the coexistence of DA and cholecystokinin (CCK). Combinations of single unit recording, microiontophoretic (or micropressure) administration of drugs, electrical stimulation, lesions by neurotoxins, radioligand receptor binding, push-pull cannula local perfusion, release of DA and CCK from brain slices, measurement of biogenic amines and CCK levels by HPLC-EC and radioimmunoassay, retrograde tracing and immunocytochemical staining techniques will be used to achieve the goals. In particular, the experiments with long-term effects of APD's will be extended to unanesthetized preparations.